Category: pro

Operaciones matemáticas

Sugerencia
Puede utilizar el intérprete de Python como calculadora. Para ello simplemente iniciar Python sin un IDE y un nombre de archivo. Ejemplo:

  Python 2.7.6 (por defecto, 22 de junio de 2015, 17:58:13) 
[GCC 4.8.2] de linux2
Tipo de "ayuda", "copyright", "créditos" o "licencia" para obtener más información.
>>> 18 * 17
306
>>> 2 ** 4
16
>>>

Funciones matemáticas

Python soporta una amplia variedad de funciones matemáticas.

Función

Devuelve

Ejemplo

ABS(x)

Devuelve el valor absoluto de x.

x = -35
x = abs(x)
Print (x)

CMP(x,y)

Devuelve -1 Si x < y
Devuelve 0 si x es igual a y
Devuelve 1 Si x > y.

x = 6
y = 4
Imprimir (cmp(x,y))

exp (x)

Devuelve la exponencial de x

importación matemáticas
x = 6
Imprimir (math.exp(x))

Cienc

El logaritmo natural de x

importación matemáticas
x = 6
Imprimir (math.log(x))

log10(x)

El logaritmo en base 10 de x

importación matemáticas
x = 6
Imprimir (math.log10(x))

Pow(x,y)

El resultado de x ** y

importación matemáticas
x = 6
Imprimir (math.pow(x,2))

sqrt(x)

La raíz cuadrada de x

importación matemáticas
x = 6
Imprimir (math.sqrt(x))

Instalar un IDE de Python

Un Entorno de escritorio integrado (IDE) es un software para la programación. Además de edición de texto simple que tienen todo tipo de funciones tales como resaltado de sintaxis, completado de código, pestañas, un explorador de la clase y muchos más.

Python online intérpretes

Los intérpretes en línea no funcionen para todo pero funcionarán para la mayoría de los tutoriales para principiantes. Recomiendo usar un IDE desktop o el interprete oficial de Python.

Resumen de IDEs (sólo necesita uno)

IDE	Autor	Plataforma	Descripción	Precio	Descargar
PyCharm	JetBrains	Windows, Mac OS X, Linux/UNIX	Python IDE. Características como: completación de código, inspecciones de código, error sobre la marcha destacando y soluciones rápidas	89 € / 1er año. ($ 97,90)	Descarga PyCharm
Átomo (+ script plugin)	GitHub	Windows, Mac OS X, Linux/UNIX	Python IDE. Necesita descargar el plugin de secuencia de comandos después de instalar el átomo.	Gratis.	Descargar Atom.
Pythonista	OMZ:software	Apple iOS (iPhone, iPad)	Las características incluyen: resaltado de sintaxis, completado de código, sistema interactivo, módulos estándar y de iOS.	€ 9. ($ 9,90)	Descargar Pythonista.
Eclipse con PyDev	Aleks Totic	Windows, Mac OS X, Linux/UNIX	Las características incluyen: sintaxis resaltado, refactorización de código, depuración gráfica y mucho más.	Gratis	Descargar
Eric Python IDE	Detlev Offenbach	Windows, Linux/UNIX	Las características incluyen: resaltado de sintaxis, autocompletado, clase navegador y más.	Gratis	Descargar
Wing IDE	Wingware	Windows, Mac OS X, Linux/UNIX	Características: Sintaxis resaltado, auto-completado, refactorización, pruebas unitarias y versión controlan.	$45 a $245 por usuario por licencia.	Descargar
Komodo IDE	Komodo	Windows, Mac OS X, Linux/UNIX	Características: Sintaxis, navegador de documentación, ejecutar código en línea, marcadores rápidos y mucho más.	€ 40 a € 223. ($99 a $295).	Descargar
Skulpt	Skulpt	Web	Intérprete de Python	Gratis	Ejecutar en línea
Repl.it	Amjad Masad, Haya Odeh, Faris Masad y Max Shawabkeh.	Web	Intérprete de Python	Gratis	Ejecutar en línea
Ideone	Ideone	Web	Intérprete de Python	Gratis	Ejecutar en línea
CodePad	Hazel de Steven	Web	Intérprete de Python	Gratis	Ejecutar en línea

SL4A: Android Python Scripting

Python scripts can be run on Android using the Scripting Layer For Android (SL4A) in combination with a Python interpreter for Android.

Related courses:
You may like:

Building Android Apps in Python Using Kivy

SL4A
The SL4A project makes scripting on Android possible, it supports many programming languages including Python, Perl, Lua, BeanShell, JavaScript, JRuby and shell. The SL4A project has a lot of contributors from Google but it is not an official Google project.

Scripts can access Android specific features such as calling, text message (SMS), take picture, text to speech, bluetooth and many more.

In this article you will learn how to run Python on Android devices using SL4A.

SL4A is designed for developers

Keep in mind that SL4A is designed for developers and in alpha quality software.

Install SL4A

First enable installation of programs from unknown sources. By default Android devices can only install apps from the Google Play Store.

You have to enable the permission ‘Install from Unknown Sources’, by going to Settings -> Security -> Unknown Sources and tap the box.

After you have have updated these settings donwload the SL4A APK. Visit https://github.com/kuri65536/sl4a on your Android device and download the SL4A APK (or use the QR code on the right).
Once downloaded an installation menu will popup, requesting all permissions on your Android device.

Install Python 3 for Android

qr-python-3-for-android — QR Code Python 3 for Android

Install the Py4A app. The Python for Android app is built to run solely on

Android devices. You should use this app together with SL4A.

You can pick any version of Py4A, but bare in mind the supported version on Android:

Python 2 requires Android Device >= 1.6
Python 3 requires Android Device >= 2.3.1

The git repository is: https://github.com/kuri65536/python-for-android/releases

You could also use the QR code on the right using a QR scanner on your Android device.

Once Py4A is installed, start the app and press install. This will install the Python interpreter.

Android-Python-3-Install — Android Python 3 Install

SL4A

Open SL4A again. Many scripts will appear (in a list). You can now run Python scripts on your Android Device!

Press on a program such as speak.py A little popup will be shown. Pressing on the terminal icon will start the Python script.

The third button (the pencil) will open an editor. This is not a full blown IDE but a simple editor.
It doesn’t have syntax highlighting.

Scripting on Android

You may prefer your favorite Python editor whatever it may be (vim/emacs fans here? PyCharm? Atom?)
All scripts are stored in /sl4a/scripts/

Note: File extension

If you installed the Python 3 interpreter, the programs will show with a .py3 extension instead of a .py extension.

A simple program (Spaceship Launch):

"""TTS Rocket Launch."""
 
__author__ = 'Frank <[email protected]>'
 
import android
 
droid = android.Android()
message = "Python on Android"
droid.ttsSpeak(message)
 
for i in range(10,0,-1):
    droid.ttsSpeak(str(i))
 
droid.ttsSpeak("We have lift off!")
droid.ttsSpeak("rrrrrr")

More examples:
http://www.mattcutts.com/blog/android-barcode-scanner/
https://github.com/damonkohler/sl4a/blob/wiki/Tutorials.md

HTTP – Parse HTML and XHTML

In this article you will learn how to parse the HTML (HyperText Mark-up Language) of a website. There are several Python libraries to achieve that. We will give a demonstration of a few popular ones.

Beautiful Soup – a python package for parsing HTML and XML
This library is very popular and can even work with malformed markup. To get the contents of a single div, you can use the code below:

from BeautifulSoup import BeautifulSoup
import urllib2
 
 
# get the contents
response = urllib2.urlopen('http://en.wikipedia.org/wiki/Python_(programming_language)')
html = response.read()
 
parsed_html = BeautifulSoup(html)
print parsed_html.body.find('div', attrs={'class':'toc'})

This will output the HTML code of within the div called ‘toc’ (table of contents) of the wikipedia article. If you want only the raw text use:

print parsed_html.body.find('div', attrs={'class':'toc'}).text

If you want to get the page title, you need to get it from the head section:

print parsed_html.head.find('title').text

To grab all images URLs from a website, you can use this code:

from BeautifulSoup import BeautifulSoup
import urllib2
 
url = 'http://www.arstechnica.com/'
data = urllib2.urlopen(url).read()
soup = BeautifulSoup(data)
links = soup.findAll('img', src=True)
 
for link in links:
    print(link["src"])

To grab all URLs from the webpage, use this:

from BeautifulSoup import BeautifulSoup
import urllib2
 
url = 'http://www.arstechnica.com/'
data = urllib2.urlopen(url).read()
soup = BeautifulSoup(data)
links = soup.findAll('a')
 
for link in links:
    print(link["href"])

PyQuery – a jquery like library for Python
To extract data from the tags we can use PyQuery. It can grab the actual text contents and the html contents, depending on what you need. To grab a tag you use the call pq(‘tag’).

from pyquery import PyQuery    
import urllib2
response = urllib2.urlopen('http://en.wikipedia.org/wiki/Python_(programming_language)')
 
html = response.read()
pq = PyQuery(html)
tag = pq('div#toc')
 
# print the text of the div
print tag.text()
 
# print the html of the div
print tag.html()

To get the title simply use:

tag = pq('title')

HTMLParser – Simple HTML and XHTML parser
The usage of this library is very different. With this library you have to put all your logic in the WebParser class. A basic example of usage below:

from HTMLParser import HTMLParser
import urllib2
 
# create parse
class WebParser(HTMLParser):
    def handle_starttag(self, tag, attrs):
        print "Tag: " + tag
 
# get the contents
response = urllib2.urlopen('http://en.wikipedia.org/wiki/Python_(programming_language)')
html = response.read()
 
# instantiate the parser and fed it some HTML
parser = WebParser()
parser.feed(html)

Python Web Development

Introduction

Web apps are often created using a framework. Frameworks make it easier to develop web apps that are scalable, reliable and maintainable. It avoids recreating the same code over and over again.
Common features are:

URL Routing
Output templates
Database management
Session management
Security against common attacks

A framework may offer some or all of these features.

For example, the Flask web application framework does not have database support and you would need a separate module to use a database. The Django web application framework supports databases by default.

Why use a web framework?

As you are doing web development, you want to avoid spending time on programming things that have already been solved. On the other hand, if you are an experienced web developer a web framework may not offer everything you need.

What Python web frameworks exist?

Django and Flask are the most popular web frameworks. However, you may want to evaluate the frameworks. An overview:

The most popular python web application framework is Django, followed by Flask.

python web development — # of projects on Github mentioning a framework.

Django

Django is the most used Python web framework. It takes care of many things so you can focus on the web app development. Sites built withDjango have dealt with high traffic spikes such as 50 thousands hits per second.

Database access is achieved through an Object-relational mapper: You define your data models in Python and Django deals with the actual database management systems (SQL). However, if you need to you can write your own SQL Queries with Django. URL routing is supported by Django. It encourages beautiful URL design such as ending without .php or .asp.

Features:

Object-relational mapper
URLs routing and views
Template engine
Forms
Authentication
Admin
Internationalization
Security

If you want to know more about Django, read here.

Did you know the websites of NASA, Bitbucket and Pinterest were made with Django?

Flask

Flask is a Python micro framework which is modular by design. The framework is intended to build web apps. Flask does not have a specific database system or ORM system. If you want to use a database, you’ll have to use extensions. Flask is often combined with SQLAlchemy for database use.

Flask is very easy to get running, a minimal app would be:

from flask import Flask
app = Flask(__name__)
 
@app.route('/')
def hello_world():
    return 'Hello World!'
 
if __name__ == '__main__':
    app.run()

The framework supports URL routing, template (using Jinja2), session management and has some out of the box security.

Features:

URL Routing and views
Template engine
Session management
Logging

If you want to know more about Flask, read here.

Did you know Flask started as an April Fools joke?

Python Hosting

To run your app on the web, you will need hosting. Unless you want to do hosting yourself, you need a party to host.
Hosting servers:

Django Getting started

Django is a high-level Python Web framework that takes care of much of the hassle of Web development, so you can focus on writing your app without needing to reinvent the wheel.

In this tutorial you will learn how to setup a basic Django web app.

Related course
Intro to Django Python Web Apps

Django tutorial

Install Django using:

pip install Django==1.7.1

Once installed, create the directory /django-hello/ for your app. In this directory create the file hello.py with this contents:

#!/usr/bin/env python
import sys
from django.conf import settings
from django.conf.urls import patterns
from django.http import HttpResponse
from django.core.management import execute_from_command_line
 
settings.configure(
DEBUG=True,
SECRET_KEY='asecretkey',
ROOT_URLCONF=sys.modules[__name__],
)
 
def index(request):
return HttpResponse('Hello, World')
 
urlpatterns = patterns('',
(r'^hello/$', index),
)
 
if __name__ == "__main__":
execute_from_command_line(sys.argv)

Execute the script using:

python hello.py runserver

A HTTP Django server will start and if you open http://127.0.0.1:8000/hello/

Django code explanation:
The top lines import the Django library:

from django.conf import settings
from django.conf.urls import patterns
from django.http import HttpResponse
from django.core.management import execute_from_command_line

If you open the link /hello/, the webserver will call the index() function. We map the url to the function using:

urlpatterns = patterns('',
(r'^hello/$', index),
)

In Django we have url friendly urls. This means you do not have a url that ends in /id=1359835, but instead we have the directory as name. Finally, we set some default settings using settings.configure.

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